Magnesium transporters E (MgtE) are a family of transmembrane eubacterial MgtE

magnesium transporter Magnesium transporters are proteins that transport magnesium across the cell membrane. All forms of life require magnesium, yet the molecular mechanisms of Mg2+ uptake from the environment and the distribution of this vital element within the organi ...

s. Related regions are found also in

archaea Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...

l and

eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s. They have sizes that vary considerably from 311 residues for the ''Methanococcus thermoautotrophicum'' protein, 463 residues for a ''

Synechocystis ''Synechocystis'' is a genus of unicellular, freshwater cyanobacteria in the family Merismopediaceae. It includes a strain, ''Synechocystis'' sp. PCC 6803, which is a well studied model organism A model organism is a non-human species ...

'' homologue, and 513 residues for the human homologue, SLC41A1. These proteins are capable of transporting Mg²⁺ and Co²⁺ but not Ni²⁺. Multiple alignments contain two

highly conserved In evolutionary biology, conserved sequences are identical or similar sequences in nucleic acids (DNA and RNA) or proteins across species ( orthologous sequences), or within a genome ( paralogous sequences), or between donor and receptor taxa ( ...

aspartate Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. The L-isomer of aspartic acid is one of the 22 proteinogenic amino acids, i.e., the building blocks of protein ...

s that may be involved in

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

binding. Human transporters from this family are

SLC41A1 SLC41A1 is a protein that in humans is encoded by the gene SLC41A1. It is homologous to the prokaryotic Mg++ transfer protein MgtE Mutations in this gene have been associated to Nephronophthisis Nephronophthisis is a genetic disorder of the kid ...

, SLC41A2 and SLC41A3.

Structure and Mechanism

The '' Bacillus firmus'' transporter and several homologues examined have strongly charged, hydrophilic N-terminal domains (cytoplasmic) followed by a hydrophobic C-terminal domain with 5 putative transmembrane α-helical spanners. A central 100 residues resembles

l inositol monophosphate dehydrogenases. Kehres and Maguire suggest that the MgtE proteins are secondary carriers with inwardly directed polarity. Hattori et al. have considered MgtE to function by a channel mechanism, providing evidence that the MgtE cytosolic domain acts as a Mg²⁺ sensor to regulate gating of the pore in response to the intracellular Mg²⁺ concentration. This produces a mechanism for the maintenance of homeostasis conditions. The cytosolic domain of MgtE undergoes a Mg²⁺-dependent structural change, which may gate the ion-conducting pore passing through the transmembrane domain. Maruyama et al. showed that MgtE exhibits the channel-like electrophysiological properties, i.e., Mg²⁺ transport occurs in accordance to the

electrochemical potential Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically conducting phase (typi ...

of Mg²⁺. The Mg²⁺-permeation pathway opens in response to a decrease of the intracellular Mg²⁺ concentration, while it is completely closed at the intracellular Mg²⁺ concentration of 10 mM. The crystal structures of the MgtE dimer reveal that the Mg²⁺-sensing cytoplasmic region consists of the N and CBS domains. The Mg²⁺-bound state adopts a compact, globular conformation, which is stabilized by the coordination of a number of Mg²⁺ ions between these domains. On the other hand, in the Mg²⁺-unbound state, these domains are far apart, and fixed by the crystal packing.

Transport Reaction

The transport reaction catalyzed by MgtE proteins is: :Mg²⁺ (or Co²⁺) (out) → Mg²⁺ (or Co²⁺) (in)

References

{{CCBYSASource, sourcepath= http://tcdb.org/search/result.php?tc=1.A.26, sourcearticle= 1.A.26 The Mg2+ Transporter-E (MgtE) Family , revision=699838558 Protein families Solute carrier family